Re: Regression in ptrace (Wine) starting with 2.6.33-rc1

["K.Prasad" <prasad@linux.vnet.ibm.com>]

On Thu, Feb 11, 2010 at 08:49:48PM +0100, Michael Stefaniuc wrote:
> On 02/11/2010 07:22 PM, Frederic Weisbecker wrote:
>> On Thu, Feb 11, 2010 at 05:33:13PM +0100, Michael Stefaniuc wrote:
>>> 2.6.33-rc1 broke ptrace for Wine, specifically the setting of the debug
>>> registers. This is visible in the Wine ntdll exception tests failing on
>>> 2.6.33-rcX while they work just fine in 2.6.32.
>>>
>>> A regression test resulted in:
>>> 72f674d203cd230426437cdcf7dd6f681dad8b0d is the first bad commit
>>> commit 72f674d203cd230426437cdcf7dd6f681dad8b0d
>>> Author: K.Prasad<prasad@linux.vnet.ibm.com>
>>> Date:   Mon Jun 1 23:45:48 2009 +0530
>>>
>>>      hw-breakpoints: modify Ptrace routines to access breakpoint registers
>>>
>
>> Thanks a lot for your report. Is there an easy way to reproduce
>> this?
> Yes, the bug is 100% reproducible. Even the "stack overflow" bytes are
> always constant on my two boxes: 932 bytes on my Atom and 1588 bytes on
> my Q9450 with a x86_64 kernel.
>
> Either grab wine-1.1.38 from
> http://sourceforge.net/projects/wine/files/Source/ or from git
>   git clone git://source.winehq.org/git/wine.git
> configure
> make
> cd dlls/ntdll/tests/
> make exception.ok
>

Can you be more specific with details - such as what was the desired
action/return value of ptrace that your testcase wanted but did not
happen (after the patch applied)? What is the other regression that
you found as a result of another patch in the hw-breakpoint patch
series?

I am able to see a user-space stackdump upon a 'make exception.ok',
which isn't easy enough (atleast for me) to narrow down to the purported
ptrace defect.

> If you build on an x86_64 machine you'll need a pretty complete 32bit
> setup too, but configure will let you know. If configure doesn't errors
> out but produces warnings, those can be safely ignored. It means the
> dependencies are optional and those aren't needed to reproduce this bug.
>
> Oh, there might be an other regression in ptrace too; introduced by a
> previous patch in this series. While bisecting i had a later test fail,
> something along the lines of "expected 4 exceptions got 0", but the
> tests completed. Now the stack corruption mask everything else in the
> tests; e.g. comment out the first test and one of the next tests will go
> into an infinite loop printing 3 Wine errors over and over again.
>
> thanks
> bye
>         michael

Thanks,
K.Prasad